Journal of Molecular Structure 1085 (2015) 235–241

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Journal of Molecular Structure

journal homepage: www.elsevier .com/ locate /molst ruc

Synthesis and structural characterization of five new copper (I)complexes with 1,10-phenanthroline and 1,4-bis(diphenylphosphino)butane(dppb)

http://dx.doi.org/10.1016/j.molstruc.2014.12.0680022-2860/� 2015 Elsevier B.V. All rights reserved.

⇑ Corresponding author. Tel.: +86 10 68903033; fax: +86 10 68902320.E-mail address: jinqh@mail.cnu.edu.cn (Q.-H. Jin).

Jian-Bao Li a, Wei-Wei Fan a, Min-Liu b, Ye-Lan Xiao a, Qiong-Hua Jin a,⇑, Zhong-Feng Li a

a Department of Chemistry, Capital Normal University, Beijing 100048, PR Chinab The College of Materials Science and Engineering, Beijing University of Technology, Beijing 100022, PR China

h i g h l i g h t s

� Crystal structures and luminescenceof five Cu(I) complexes were studied.� Complex 4 is of the infinite zigzag

chain that forms by hydrogen bondsN� � �HAO.� In complex 5, dppb acts as bridging

ligand to form 1D supramolecularstructure.� Different anions can regulate and

control the emitting colors ofcomplexes 1–5.

g r a p h i c a l a b s t r a c t

a r t i c l e i n f o

Article history:Received 9 August 2014Received in revised form 21 November 2014Accepted 22 December 2014Available online 7 January 2015

Keywords:Copper(I) complexes1,4-Bis(diphenylphosphino)butane (dppb)Luminescent

a b s t r a c t

The mixture of copper(I) salts CuX (X = Cl, Br, SCN, CN, SO3CF3) and 1,10-phenanthroline (phen) reactswith 1,4-bis(diphenylphosphino)butane (dppb) to give dinuclear complexes [Cu2(dppb)(phen)2Cl2]-�4DMF (1), [Cu2(dppb)(phen)2Br2]�DMF (2), [Cu2(dppb)(phen)2(SCN)2] (3) and two 1D chain complexes{[Cu2(dppb)(phen)2(CN)2(H2O)]}n�nH2O (4) and {[Cu2(dppb)(phen)2](SO3CF3)2}n (5), respectively. Thestructures of these compounds were investigated by elemental analysis, single-crystal X-ray diffraction,electronic absorption spectroscopy, fluorescence spectroscopy, 1H NMR and 31P NMR spectroscopy. EachCu atom adopts a distorted tetrahedral configuration, and all the complexes are considerably air-stable insolid state and in solution. Detailed NMR studies have been performed to disclose the behavior of theprepared copper(I) complexes in solution. All the five complexes are bright green and cyan luminophoresin a solid state at room temperature. This makes them potential candidates as cheap emitting materialsfor electroluminescent devices.

� 2015 Elsevier B.V. All rights reserved.

Introduction

Copper(I) complexes have been widely studied in view of theirintriguing photophysical properties and promising applications in

organic light-emitting devices, dye-sensitized solar cells, andluminescence sensors. Especially heteroleptic Cu(I) compoundscontaining phosphines and N-donor ligands attract much attentiondue to their low cost, nontoxicity and luminescence [1–8]. Amongthem mononuclear and binuclear Cu(I) complexes containingdiphosphine ligands and nitrogen ligands have been the focus ofmuch investigation [9–11]. In 2009, Fu and his coworkers reported

236 J.-B. Li et al. / Journal of Molecular Structure 1085 (2015) 235–241

a series of dinuclear copper(I) complexes, which have shortCu� � �Cu separations [12]. In 2013, Chen and his coworkers reporteda series of mononuclear heteroleptic copper(I) complexes, whichhave good photophysical properties [13].

As far as we know, Cu(I) supramolecular complexes are verydifficult to synthesize because of the insolubility of Cu(I) salts inorganic solvent and their instability in water and air. To synthesizeCu(I) supramolecular complexes, we need to find a suitable mainorganic ligand that can act as a bridging ligand and enhance thestability of Cu(I) complexes. Among the multi-functional ligands,dppb is a good candidate as the main ligand because, due to itsbridging tendency, it is very suitable to lock two Cu(I) atomstogether in close proximity to form an Cu2(dppb) core structure[14].

In our previous work, a number of mixed-ligand coordinationcompounds of copper(I) salts with heterocyclic nitrogen ligandand diphosphane were prepared and structurally characterized[15,16]. Especially we synthesized a series of 1D chain supramolec-ular complexes which is constructed through intermolecular hydro-gen bonds [17]. In this paper, we choose dppb as bridging ligand toform 1D chain structure, choose phen as coligand to enhancefluorescence effect, and use copper (I) salts which have differentanions. We successfully synthesized a series of new Cu(I) com-plexes—three dinuclear complexes [Cu2(dppb)(phen)2Cl2]�4DMF(1), [Cu2(dppb)(phen)2Br2]�DMF (2) and [Cu2(dppb)(phen)2(SCN)2](3), two 1D chain complexes {[Cu2(dppb)(phen)2(CN)2(H2O)]}n�nH2O (4) and {[Cu2(dppb)(phen)2](SO3CF3)2}n (5) (Scheme 1). Thecomplexes 1–5 can be used as green and cyan emitter component,whose color can be tuned by choosing different anions. This makesthese complexes more intriguing.

Experimental

Materials and measurements

All chemical reagents are commercially available and usedwithout further purification. Elemental analyses (C, H, N) weredetermined on a Vario EL elemental analyzer. Infrared spectra wererecorded on a Nicolet Avatar 360 FT-IR spectrometer using the KBrpellet in the range of 400–4000 cm�1. Inductively coupled plasma(ICP) spectroscopy was performed on an Agilent 7500Ce spectrom-eter. UV–Vis spectra of samples in CH2Cl2 solution were recordedon a UV-2450 spectrometer at room temperature. Excitation andemission spectra of the solid samples were recorded on anF-4500 fluorescence spectrophotometer at room temperature. 1HNMR was recorded in CDCl3 solution at room temperature with a

Scheme 1. The routine of syn

Bruker DPX 600 MHz spectrometer and 31P NMR was recorded atroom temperature with a Bruker DPX 400 MHz spectrometer.

Synthesis of complex 1

A mixture of CuCl (29.7 mg, 0.3 mmol) and dppb (63.97 mg,0.15 mmol), 1,10-phen (59.4 mg, 0.3 mmol) were dissolved in amixture of CH2Cl2 (7 ml) and DMF (3 ml), stirred for 4 h. Theinsoluble residues were removed by filtration, and the filtratewas evaporated slowly at room temperature for a week to yieldyellow crystalline products. Yield: 70%. Anal. Calc. For C64H72Cu2

N8O4P2Cl2: C, 60.18, H, 5.68, N, 8.77, Cu, 8.95. Found: C, 62.50, H,5.61, N, 8.79, Cu, 10.02. IR (KBr disc, cm�1): 3442 m, 3047w,1662s, 1578w, 1437s, 1390m, 1257w, 1142w, 1095m, 1029w,997w, 880w, 852s, 783w, 749m, 731s, 700s, 658w, 633w, 508m,491w, 416w.

Synthesis of complex 2

Complex 2 was prepared in a manner similar to that describedfor 1, except that CuBr (43.0 mg, 0.3 mmol) was used as the start-ing materials. After three days, yellow crystals were formed. Yield:78%. Anal. Calc. For C55H51Cu2N5P2OBr2: C, 57.60, H, 4.48, N, 6.11,Cu, 9.37. Found: C, 57.53, H, 4.47, N, 6.09, Cu, 11.16. IR (KBr disc,cm�1): 3437w, 3044w, 1620m, 1586m, 1507s, 1482s, 1434s,1421s, 1139w, 1097m, 846s, 741s, 729s, 698s, 633w, 520s, 483 m.

Synthesis of complex 3

Complex 3 was prepared in a manner similar to that describedfor 1, except that CuSCN (36.5 mg, 0.3 mmol) was used as the start-ing materials. After three days, yellow crystals were formed. Yield:70%. Anal. Calc. For C54H42Cu2N6P2S2: C, 63.69, H, 4.39, N, 7.96, Cu,10.78. Found: C, 63.00, H, 4.08, N, 8.17, Cu, 12.45. IR (KBr disc,cm�1): 3441 m, 3051w, 2929w, 2081s, 1622w, 1587w, 1481w,1434s, 1422s, 1141s, 1121s, 1099s, 998w, 881w, 843s, 750s,728s, 697s, 626m, 517m, 482w.

Synthesis of complex 4

Complex 4 was prepared in a manner similar to that describedfor 1, except that CuCN (26.9 mg, 0.3 mmol) was used as the start-ing materials. After three days, yellow crystals were formed. Yield:67%. Anal. Calc. For C54H48Cu2N6O2P2: C, 64.73, H, 4.83, N, 8.39, Cu,10.98. Found: C, 64.65, H, 4.76, N, 8.41, Cu, 12.77. IR (KBr disc,cm�1): 3599w, 3406w, 2100s, 1638m, 1620m, 1585m, 1571m,

thesis for complexes 1–5.

Table 1Crystallographic data for complexes 1–5.

Compound 1 2 3 4 5

Empirical formula C64H72Cl2Cu2 C55H51Br2Cu2 C54H42Cu2N6 P2S2 C54H48Cu2 C43 H39CuN8O4P2 N5P2O N6P2O2 F3N3O3P2S

Formula weight 1277.22 1146.85 1028.08 1002.00 860.31Crystal system Triclinic Monoclinic Triclinic Monoclinic MonoclinicSpace group P�1 C2/c P�1 P2(1)/c C2/c

a (ÅA0

) 11.7670(12) 16.6530(17) 8.8500(10) 12.0713(12) 12.4510(14)

b (ÅA0

) 11.8780(13) 17.0879(19) 12.5429(15) 12.3565(11) 25.710(3)

c (ÅA0

) 12.7060(15) 19.195(2) 13.0341(17) 16.5533(14) 25.780(2)

b (�) 81.082(8) 94.1000(10) 75.595(2) 103.3240(10) 91.6000(10)

V (ÅA0

3) 1574.2(3) 5448.3(10) 1222.2(3) 2402.6(4) 8249.4(14)

Z 1 4 1 2 8Dcalc (g/cm3) 1.347 1.398 1.397 1.385 1.385l (mm�1) 0.864 2.348 1.064 1.000 0.714T (K) 298(2) 298(2) 298(2) 298(2) 298(2)Ra 0.0444 0.1121 0.0489 0.0370 0.0913xR2

b 0.1114 0.2871 0.1335 0.1009 0.1595

a R =P

(|F0|�|Fc|)/P

|F0|.b xR2 = [

P(x|F0|2�|Fc|2)2/

Px|F0|2]1/2.

Fig. 1. The molecular entities of complex 1. Thermal ellipsoids drawn at the 50% probability level. All of the H-atoms and DMF molecules are omitted for clarity.

J.-B. Li et al. / Journal of Molecular Structure 1085 (2015) 235–241 237

1508s, 1480m, 1459s, 1435s, 1223w, 1173m, 1097s, 997w, 951s,854s, 783m, 749s, 698s, 633m, 515s, 485m, 444w.

Synthesis of complex 5

A mixture of Cu(SO3CF3)2 (54.25, 0.15 mmol) and Cu(9.525 mg,0.15 mmol) were dissolved in 15 ml CH3CN. After stir-ring for 0.5 h at room temperature, dppb (63.97 mg, 0.15 mmol)and 5 ml CH2Cl2 was added to the mixture which was stirred forfurther 2 h. Then another ligand phen (59.4 mg, 0.3 mmol) wasadded and a yellow powder of the mixed-ligand complex {[Cu2

(dppb)(phen)2](SO3CF3)2}n was given. Yield: 50%. Anal. Calc. For:C43H39CuF3N3O3P2S: C, 60.03, H, 4.57, N, 4.88, Cu, 6.78. Found: C,60.12, H, 4.54, N, 4.79, Cu, 7.44. IR (KBr disc, cm�1): 3452m,3056w, 2919w, 2850s, 1625w, 1587w, 1511w, 1482w, 1435s,1271s, 1224w, 1100s, 1031s, 879w, 850s, 805w, 780w, 730s,694s, 637s, 516m, 482m.

Single crystal X-ray crystallography

Single-crystal X-ray diffraction studies of complexes 1–5 wereperformed on a Bruker SMART diffractometer equipped with CCDarea detector with a graphite monochromator situated in the inci-dent beam for data collection. The determination of unit cellparameters and data collections were performed with Mo ka radi-ation (k = 0.71073 ÅA

0

) by x scan mode. All data were corrected by

semi-empirical method using SADABS program. The programSAINT was used for integration of the diffraction profiles. All struc-tures were solved by direct methods using SHELXL program of theSHELEX-97 package and refined with SHELXL-97 [18]. Metal atomcenters were located from the E-maps and other non-hydrogenatoms were located in successive difference Fourier synthesis.The final refinements were performed by full-matrix least-squaresmethods with anisotropic thermal parameters for non-hydrogenatoms on F2 [19]. All the hydrogen atoms were first found indifference electron density maps, and then placed in the calculatedsites and included in the final refinement in the riding modelapproximation with displacement parameters derived from theparent atoms to which they were bonded.

Two of DMF molecules in each complex 1 unit are disorderedover two positions. The occupancies of each set of atom coordi-nates refined to values of 0.527 and 0.473, respectively. DMFmolecules in 2 also show disorder with occupancies of 0.5 and0.5. In complex 3, the restraint command ‘‘DFIX’’ and ‘‘DELU’’was applied to the disordered C24, C25, C26, C27 and C28 atomsfor obtaining reasonable thermal parameters. Atoms C24, C25,C26, C27 and C28 of the phenyl group in 3 show disorder withoccupancies of 0.68 and 0.32. The dppb group (C15 and C16) showsdisorder with occupancies of 0.50 and 0.50. In complex 4, therestraint command ‘‘DFIX’’ was also applied to the N3 and O1atoms. In complex 5, the restraint command ‘‘ISOR’’ was appliedto the C35, C39, C40 and C41 atoms, the restraint command ‘‘DFIX’’

Fig. 2. Perspective view of the linear one-dimensional chain of 4. The intermolecular hydrogen bonds N� � �HAO are shown with dashed lines. Water of crystallization but theatoms involved in H-bonding is omitted, and phenyl of dppb is omitted for clarity.

238 J.-B. Li et al. / Journal of Molecular Structure 1085 (2015) 235–241

was applied to the C15, C16, C21, C26, F1, F2, F3, O1, O2, O3 and S1atoms, and the restraint command ‘‘DELU’’ was applied to theseveral atoms such as C41, F1, F2, F3 and S1 atoms for obtainingreasonable thermal parameters.

As to compound 3, we have described the disorder of dppbunits. However, we did not measure it at low temperature, so theS atoms inevitably exit thermal vibration phenomenon. To ourrelief, we have refined compound 3, making its R-factor lower.Unfortunately, for 2 and 5, seriously thermal displacement wasobserved for DMF and counterions SO3CF3

� molecules of the crys-talline solvent. And we try our best to make their R-factor lower.Although the quality of the data became quite poor, there wassufficient precision for the molecules of 2 and 5 to enable its char-acterization and starting structure for optimization. The reason forhigh R values is the quite high thermal displacement of the crystal-line solvent molecules. As is often the case with crystal structureanalysis, crystalline solvent molecules fixed weakly with intermo-lecular van der Waals forces or hydrogen bonds indicate seriousthermal motion in the space made from the main crystal frame-work of complex molecules, whilst the important part of complexmolecules are finely analyzed without any problems for thepresent purpose and precision, namely confirming the chemicalstructure prepared. A summary of the crystallographic data anddetails of the structural refinements are listed in Table 1. Selectedbond distances and bond angles are listed in Table S1.

Results and discussion

General aspects

Copper(I) complexes 1–4 were prepared by reactions ofcopper(I) salts CuX (X = Cl�, Br�, SCN� or CN�) with 0.5 equiv ofdppb and 1 equiv of 1,10-phen in the mixture of dichloromethane(CH2Cl2) and dimethylformamide (DMF) under ambient condi-tions. Complex 5 was synthesized by treatment of Cu(SO3CF3)2

and copper powder in CH3CN solution, followed by the additionof 1 equiv of dppb and CH2Cl2 solution, and 2 equiv of 1,10-phen.

The molar ratio of CuX:dppb:phen (2:1:2) is very important forthe generation of [Cu2(dppb)(phen)2X2](X = Cl, Br, SCN, CN, SO3-

CF3). If the molar ratio of 1:1:1 was employed, we cannot get thesingle crystals. Because the coordination ability of dppb ligand isstronger than 1,10-phen, the excess of dppb will coordinate withthe Cu atom. In each of complexes 1–4, the anion acts as ligand,but in complex 5, anion SO3CF3 acts as the counter anion.

The mixed solvent also plays an important role in the synthesisof copper(I) complexes. The complexes 1–4 were formed in the

mixed solvent of CH2Cl2 and DMF, complex 5 was formed in themixed solution of CH3CN and CH2Cl2.

In order to obtain a full series of complexes, we studied thereaction of CuI with phen and dppb in the mixed solvent of CH2Cl2

and CH3CN or the mixed solvent of CH2Cl2 and CH3OH. Unfortu-nately, our efforts to prepare the corresponding iodide complex[Cu2(dppb)(phen)2I2] was unsuccessful.

Single crystal X-ray studies

Crystal structure of complexes 1–3Crystallographic data and crystal refinement parameters are

shown in Table 1. Selected bond angles and bond distances aregiven in Table S1. The perspective views of 1–3 are shown inFig. 1, Figs. S1 and S2, respectively. Complexes 1–3 are dppb-bridged dimer of Cu(I). Cu atom has a 4-coordination sphere, it iscoordinated with two N atoms from the 1,10-phen ligand, oneCl- (Br- or SCN-), and one P atom from dppb. It should be notedthat Cu(phen)(dppb) tends to form dimeric complexes with twoP atoms serving as bridge between the two copper atoms [20].The symmetry unit of 1 contains one molecule of Cu2

(dppb)(phen)2Cl2 and four isolated molecule of DMF. Complexes1 and 2 have the same structure and complex 2 contains one mol-ecule of Cu2(dppb)(phen)2Br2 and one isolated molecule of DMF.With regard to complex 3, the C15 and C16 of dppb were modeledas disordered around two positions in a 0.5:0.5 ratio. The anglesaround Cu ranging from 79.0(1)� to 120.0(4)� in 1, from 76.5(1)�to 123.3(1)� in 2, from 79.6(2)� to 125.8(1)� in 3, which indicatethat the geometry around the CuN2PX core is approximately tetra-hedral. In complexes 1–3, the angles of NACuAP are different fromthat observed in [Cu2(dppm)(phen)2(SCN)2] [21] (99.7(1)� to138.3(4)�). The mean bond distances of CuAP in 1–3 are 2.205 ÅA

0

,2.174 ÅA

0

and 2.207 ÅA0

respectively, which are shorter than those incomplexes [Cu2(l-dppb)2(CH3CN)4](BF4)2 (2.271 ÅA

0

) [22] and [Cu2

(dppb)2(dmp)2](PF6)2 [23] (2.278 ÅA0

). The CuAP distance in 2 isshorter than that in 1, due to the decreased electron-donatingcharacter of the halide (Cl� > Br��). In compound 2, CuAN lengthsare in the range of 2.150(2)–2.160(2) ÅA

0

, which are longer thanthose in the literature [21]. The CuAN lengths in 3 are in rangeof (1.979(4)–2.091(3) ÅA

0

), which are shorter than those in 1–2(2.098(3)–2.159(3) ÅA

0

for 1, 2.150(3)–2.160(3) ÅA0

for 2).

Crystal structure of complexes 4–5X-ray diffraction analysis reveals that complex 4 is monoclinic

in P2(1)/c space group, while complex 5 is monoclinic in C2/c spacegroup. In compound 4, the Cu(I) is coordinated to one phosphorus

Fig. 3. (a) Perspective view of the linear one-dimensional chain of 5. Omit all of the other H-atoms and phenyl of dppb. (b) Perspective view of a two-dimentional (2D) layersstructure of 5.

J.-B. Li et al. / Journal of Molecular Structure 1085 (2015) 235–241 239

atom from dppb, two nitrogen atoms from the ligand 1, 10-phenand one C atom from CN (Fig. S3). The O-H group of H2O isconnected to the N atom of CN group by the hydrogen bonds ofN3� � �H1CAO1 [O1AH1C� � �N3 = 169.3(2)�, N3� � �O1 = 3.338(4) ÅA

0

] andN3� � �H1DAO1 [O1AH1D� � �N3 = 168.6(3)�, N3� � �O1 = 2.929(5) ÅA

0

](Fig. 2). The NAH bond length is in the range of 2.091–2.500 ÅA

0

,which are comparable with that in the literature [24]. This modeof intermolecular association between CN and H2O leads to theformation of 1D structure. The other water molecule is isolatedin the solvent. Unlike complex 4, the copper(I) atom in complex

5 is coordinated by two nitrogen atoms and two phosphorus atomsof two different dppb (Fig. 3a). In 5 each two copper atoms arebridged by two P atoms of dppb to form an infinite 1D chain.Moreover, it is noteworthy that each OTf– anion is attached inrespectively left and right directions to the two {[Cu2(dppb)(phen)2] units through CAH� � �F and CAH� � �O hydrogen bonds(Fig. 3b). The hydrogen bonds connected to OTf� are C1AH1. . .O1

[C1AH1� � �O1 = 140.8(8)�, C1� � �O1 = 3.367(18) ÅA0

], C3AH3� � �O3 [C9AH9� � �O3 = 131.5(9)�, C9� � �O3 = 3.175(21) ÅA

0

], C13AH13A� � �F2 [C13AH13A� � �F2 = 148.8(7)�, C13� � �F2 = 3.506(20) ÅA

0

], C13AH13B� � �F2

Fig. 4. Absorption spectra of respective complexes 2–4 in diluted CH2Cl2 solution atambient temperature.

Fig. 5. The luminescent emission spectra of 1–5 in the solid state at roomtemperature.

240 J.-B. Li et al. / Journal of Molecular Structure 1085 (2015) 235–241

[C13AH13B� � �F2 = 155.7(7)�, C13� � �F2 = 3.302(20) ÅA0

] and C2AH2� � �F3

[C2AH2� � �F3 = 138(1)�, C2� � �F3 = 3.302(24)]. These bonds anddppb-bridged result in a two-dimentional (2D) layers structure.The CuAP distances in 5 is 2.243(1) ÅA

0

, which is shorter than thosein complex {[Cu2(dppe)2(phen)2](ClO4)2(CH2Cl2)}n (2.248(5)–2.279(5) ÅA

0

) [16]. The CuAN distances (2.048(2)–2.106(2) ÅA0

) in 5are similar with those in the literature [15] (2.069(1)–2.120(1) ÅA

0

).The NACuAN angle of {[Cu2(dppe)2(phen)2](ClO4)2(CH2Cl2)}n

(80.2�(7)) is somewhat greater than that of 5 (79.0(9)�) becauseof the reduced steric congestion of dppe relative to dppp. ThePACuAP angles in 5 (115.1(4)�) is remarkably smaller than thatin {[Cu2(dppe)2(phen)2](ClO4)2(CH2Cl2)}n (121.4(2)�).

Photophysical properties of complexes 1–5The UV–vis absorption spectra of the complexes 2–4 were

recorded in a CH2Cl2 solution at 298 K, and they are shown inFig. 4. The complexes 2–4 exhibit a comparatively weak low-energy absorption tail (e < 1000 M�1 cm�1) in the range of 300–380 nm. The lowest-lying transition of complexes 2–4 most likelyattributing to MLCT transition from the dp orbital of the (3d10)Cu center to the unoccupied p⁄ orbital of the phen ligand andmixed with some halide-to-ligand charge-transfer (XLCT) charac-ter for 2.

Photoluminescence properties of coordination d10 metalcomplexes have been widely investigated with the purpose ofdeveloping light-emitting materials and devices [25–27]. Herewe investigated the solid-state luminescence of the copper(I)complexes 1–5 by comparing them with the metal-free dppband phen ligands. The dppb and phen ligands show weak emis-sion at around 441 and 420 nm, respectively, in the solid state atroom temperature. The fluorescence emissions of 1–5 are shownin Fig. 5. When these complexes are excited (at 490 nm for 1, at470 nm for 2, at 445 nm for 3, at 457 nm for 4, at 460 nm for 5),they all display strong fluorescence effect (the emission peak isat 537 nm for 1, 524 nm for 2, 493 nm for 3, 514 nm for 4,560 nm for 5). The above data indicate that complexes 1–5 havesimilar excitation and emission spectra, and the emission wave-lengths are red shifted compared with those of the correspond-ing free ligands, which leads to a visible emission colorchange. Absorption maxima at around 300 nm and emissionsaround 450–510 nm are typical of CuAP containing chromoph-ores with either ILCT (r-ap) or MLCT (d-r⁄) excited states[28]. Therefore, the big shifts of the emission wavelengths indi-cate that the luminescence of the copper(I) complexes 1–5 areascribed to metal-to-ligand charge transfer (MLCT) between thecopper(I) atoms and the phen ligand. The halogen could affectthe emission spectra in the form of a ligand-to-metal charge-transfer (XMCT) or an interligand charge-transfer (XLCT, X ? Cl,Br) [29]. The kmax values of binuclear complexes 1, 2 are inthe order 1 > 2, which is consistent with the order of ligand fieldstrength of the halogen ions in the complexes (Br� < Cl�). How-ever, complexes 3 and 4 exhibit an intense high-energy emissionwith kem at 493 nm, 514 nm, which are slightly blue-shifted withrespect to the complexes 1 and 2. This may be due to the effectof the anion thiocyanate and cyanide. Complex 5 displays a low-energy emission with kem at 560 nm, which is remarkably red-shifted compared with that of free ligands dppb and phen. Fromthe above results, we can conclude that dppb and phen ligandsare sensitizers for luminescence of 1–5, and the complexes 1–5act as green and cyan emitter component. Consequently, differ-ent anion can affect the emitting color of complexes.

NMR spectra of complexes 1–5The 1H NMR spectra and 31P NMR spectra of complexes 1–5

have been measured in the CDCl3 solution. The 1H NMR spectraof complexes 1–5 are consistent with the binuclear structure.The resonance signals at range 7.0–8.2 ppm are assigned to theprotons of dppb and phen in the solution of 1–5. The aromatic pro-tons of dppb in 1–5 are in the range of 7.1–7.5 ppm, 7.0–7.4 ppm,7.1–7.4 ppm, 7.0–7.4 ppm and 7.0–7.5 ppm, respectively. Theseindicate that the environments of the ligands dppb in these fivecomplexes are similar. The protons signals of phen in 1–5 arealmost identical and they are in the range of 7.6–8.0 ppm (1),7.9–8.2 ppm (2), 7.6–7.9 ppm (3), 7.8–8.1 ppm (4) and 7.7–8.8 ppm (5) respectively. For 1–5, the signals of CH2 protons arein the range of 1.7–1.8 ppm, 1.4–1.6 ppm, 1.4–1.9 ppm, 1.5–1.8 ppm and 1.3–2.6 ppm respectively. The difference of signalsin 1–4 may be attributed to the difference of anions (Cl�, Br�, SCN�

and CN� for 1–4, respectively). While in compound 5 the trifluo-romethane sulfonic anion acts as counter anion to balance thesolution charge, which may result in the distinction of signals.

In each 31P NMR spectrum of complexes 1–5, only a single res-onance signal was found. This suggests that each copper(I) com-plex with dppb and phen is symmetric molecular and allphosphorus atoms in each molecule are chemically equivalent[30]. The complexes 1–5 are symmetric molecule. The correspond-ing phosphorus resonances for 1–5 are at 31.9 ppm (1), 46.7 ppm(2), 45.1 ppm (3), 34.1 ppm (4), 50.6 ppm (5) respectively. Obvi-ously, the 31P NMR chemical shifts in the compounds are similar

J.-B. Li et al. / Journal of Molecular Structure 1085 (2015) 235–241 241

due to the similar electronic situation in the phosphorus nuclei andenvironment in these crystals.

Conclusion

Five copper(I) complexes have been synthesized and character-ized by elemental analysis, X-ray diffraction, NMR, luminescence.In complexes 1–4, dppb acts as the bridging ligand and is coordi-nated by the two P atoms. Phen acts as a bidentate ligand and iscoordinated by the two N atoms. Besides, the anion Cl�, Br� SCN�

and CN� act as ligands to form the binuclear complexes [Cu2

(dppb)(phen)2X2] (X = Cl�, Br� SCN� and CN�). Complex 4 formsan infinite zigzag chain by intermolecular hydrogen bondsN� � �HAO. The complex 5 forms 1D supermolecular through thecoordination dppb ligand. Complexes 1–5 exhibit emission in thesolid state at ambient temperature, which can be assigned to 3ILCT(or 3MLCT) transitions. Consequently, different anion can regulateand control the emitting color of complexes.

Acknowledgements

This work has been supported by the National Natural ScienceFoundation of China (Grant Nos. 21171119, 11104360 and11204191), the National High Technology Research and Develop-ment Program 863 of China (Grant No. 2012AA063201) and theCommittee of Education of the Beijing Foundation of China (GrantNo. KM201210028020), Scientific Research Base DevelopmentProgram of the Beijing Municipal Commission of Education.

Appendix A. Supplementary material

CCDC 899896, 806136, 806138, 806137, 899894 contain thesupplementary crystallographic data for complexes 1–5,respectively. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from theCambridge. Crystallographic Data Centre, 12 Union Road,Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:deposit@ccdc.cam.ac.uk. Supplementary data associated with thisarticle can be found, in the online version, at http://dx.doi.org/10.1016/j.molstruc.2014.12.068.

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